In many situations it is desirable that a screw be securely attached to a screwdriver. Such an arrangement enables the operator to place the screw into the screw hole with one hand because it is not necessary to use a hand to hold the screw on the driver. Further, when firmly attached, “buckling” of the screw-screwdriver assembly can be prevented if the operator accidentally tries to drive the screw slightly off-angle. In addition, in some situations when trying to place a screw down into a small hole, there sometimes is not room for the operator's finger to hold the screw on the end of the screwdriver. For example, in the case of surgical screws, once the screw and driver are turned downward into the surgical wound, if the screw falls off the driver, it can be lost in the wound. Further in regard to surgical screws, when working under poor visualization due to a limited dissection and other causes of poor exposure (e.g., minimally invasive surgery), if the screw misses the predrilled hole and slips off the bone, it can plunge into the surrounding muscle. Likewise, when the screwdriver is pulled back it leaves the screw in the surrounding tissue if the screw is not firmly attached to the driver. Retrieving such a lost screw can be extremely problematic.
Although many attempts have been made to provide secure attachment of screws to their drivers, almost all of these devices function by providing “fingers” disposed around the screwhead that grasp the screw and hold it on the driver. Some such devices are stoutly designed and might function to hold the screw securely, but they do so at the cost of being large and bulky, which is especially undesirable in minimally invasive surgery. In addition, such devices are frequently exceedingly complex and would not tolerate surgical autoclaving. Also, such fingers tend to become caught under the head of the screw when it is fully inserted. When the fingers catch under the head of the screw in this way, the screw must be loosened to remove the fingers and then retightened. Thus, although such devices are currently in use in orthopedic surgery, they have significant limitations.
Alternatively, some devices function by having a hexagonal tip screwdriver in which the tip expands within the head of the screw thus gripping the hex socket in the screw from the inside. This kind of fixation is not very secure, however, and such devices are known to drop screws in use. They can also require multiple hands to assemble the screw to the screwdriver (e.g., one holds the screw, another holds the driver, a third tightens the ring that expands the tip of the screwdriver).
Some devices are designed to be used with special screws that have internal threads on the heads of the screws. Thus, compared to the hexagonal tip devices, these systems can provide more secure fixation, but they can still have the disadvantage of requiring that the operator tighten the screw onto the driver (e.g., a three hand operation), then assemble the driver onto the power driving tool before using it. Then, after insertion of the screw, the power tool must be removed from the driver to allow the bolt that holds the screw on the driver to be removed, and this removal step can often require the use of even another tool to loosen the bolt.
Accordingly, although a variety of different screwdriver designs have been used to address the problem of screw-screwdriver fixation, each of these designs has significant flaws. As a result, it would be desirable for apparatuses and methods to be developed for securely yet releasably holding a screw on a screwdriver.